1. Field of the Invention
The present invention relates to a clamping apparatus and, more particularly, to a clamping apparatus for holding a wheel rim during a working process.
2. Description of the Related Art
A conventional clamping apparatus for holding a wheel rim comprises a chuck, a drive shaft connected with the chuck, and a plurality of positioning modules mounted on the chuck. The positioning modules are arranged in a radiating manner along the axial direction of the chuck. Each of the positioning modules includes a clamping claw, a sleeve and a restoring spring. The sleeve and the restoring spring are mounted on the clamping claw respectively. When in use, the wheel rim is mounted on the chuck. Then, the positioning modules are extended outward to abut the inner wall of the wheel rim. Then, the drive shaft is driven to drive and rotate the chuck so as to proceed a turning and cutting process of the wheel rim. Usually, the conventional clamping apparatus comprises many positioning modules to increase the holding force so as to prevent the wheel rim from being loosened during the working process. However, too many positioning modules apply a greater pressure on the wheel rim so that the inner wall of the wheel rim is easily distorted or deformed due to the excessive pressure of the positioning modules, thereby decreasing the working efficiency, precision and quality of the wheel rim, and thereby causing a waste of material.